The birth of a baby is expected to be a time of joy and happiness. Unfortunately, what is expected does not always occur. According to the latest National Center for Health Statistics report, there were 4,040,121 births in the United States last year.1 Of these, 7.6 percent were considered low birth weight (LBW) babies (< 2,500 g). The average weight of a full-term baby is 3,400 g.
Among the potential complications of a LBW newborn, respiratory infections are a major concern. One of the most contagious lower respiratory tract infections is respiratory syncytial virus (RSV). But thanks to a new drug on the market that studies have found to be both safe and effective in preventing RSV, this concern may soon be greatly reduced.
In 1956, Morris, Blount and Savage published a paper on a pathogen that caused upper respiratory infections in chimpanzees.2 When Dr. Blount himself was accidentally infected with the same pathogen, its name was changed from chimpanzee coryza (sneezing and rhinorrhea) virus to RSV, since the cells infected with the virus have a tendency to fuse together and form syncytia with no distinct cellular margins.
RSV has been determined to be a highly contagious virus. It is the most common cause of bronchiolitis and pneumonia among infants and children under 1 year of age.3 Approximately two-thirds of infants are infected with RSV by their first birthday and almost 100 percent by the age of 3. The majority of those infected who require hospitalization are under the age of 6 months. Most children recover within 8-15 days.
A nationwide estimate places RSV infections that result in hospitalizations at almost 125,000.4 The Institute of Medicine estimates that nearly 2 percent of hospitalized children die from this disease.5 Re-infection is a common occurrence as being infected once does not offer long-lasting immunity. It is not unusual for infants to have infections in several successive RSV seasons.
RSV is transmitted through infectious secretions (droplet infection) as a result of close contact with either an infected person or contaminated surfaces such as bedclothes or facial tissues. Viral shedding6 also makes the spread of RSV almost unavoidable. Viruses are capable of traveling along nerve fibers to the skin and mucous membranes and become contagious 24-48 hours before any symptoms occur. This can also last for as long as 2 weeks after symptoms begin. For most patients, the incubation period is 3-5 days.
In temperate climates, RSV infections usually occur during annual community outbreaks, often lasting 4-6 months during the late fall, winter or early spring months.7 Being aware of the risk factors for RSV infection as well as the timing of the peak RSV infection season in your region can greatly reduce the spread of the disease.
Factors that increase the risk of RSV infection are shown in Table 1.
RSV is typically presented as a common viral respiratory infection with a 2-3 day prodromal phase. It causes nasal stuffiness and discharge. A low-grade fever also may be present. These symptoms may last for 1-2 weeks. A cough, which may go beyond that, also can occur. In general, once a person has been exposed to RSV the symptoms develop in less than 1 week.
Once exposed and infected with RSV, the contagious period is usually 10 days after the symptoms begin. RSV bronchiolitis does, however, have distinct symptoms:
wheezing and cough;
irritability and restlessness;
fever as high as 104ºF if another illness, such as otitis media, is present;
nasal flaring and intercostal, subcostal and sternal retractions; and
circumoral and nail-bed cyanosis may be present in infants with severe disease.
Most patients who develop bronchiolitis have a resolution of symptoms in approximately 1 week.
While RSV is usually diagnosed based on the appearance of symptoms, there are laboratory methods available. Proper testing will rule out bacterial infection and positively identify RSV. Various methods can be used to detect the virus, such as virus isolation, detection of viral antigens, detection of viral RNA, a demonstrable rise in serum antibodies, or a combination of these. Since the results of direct antigen testing can be made within hours, it is the preferred method of testing.
As with most infectious situations, the first preventive measure is careful and frequent hand.washing. It is not uncommon for a child to be infected before symptoms appear. Parents should use the following guidelines to help in the prevention of RSV.
Wash hands with soap and warm water before touching the baby;
Do not permit smoking near the baby;
Do not allow contact with the baby of anyone with a cold or fever;
Do not take the baby into crowded locations such as malls and stores;
Properly dispose contaminated items such as tissues.
In a hospital setting, any infected infants must be cohorted to prevent large-scale outbreaks of nosocomial infections. The mean cost of an RSV hospitalization is approximately $27,101. Depending on the length and severity of the illness, these costs can range from $2,025 to $166,375.8
The FDA has approved two products for the prevention of RSV disease in children less than 2 years old who have pulmonary problems due to either prematurity or bronchopulmonary dysplasia. RespiGam® (respiratory syncytial virus immune globulin intravenous-human, MedImmune Inc.) is a polyclonal antibody administered intravenously monthly over 4-6 hours during the course of the RSV season. Synagis® (palivizumab, MedImmune Inc.) is given intramuscularly during the course of the season. Due to the ease of administration and concern of fluid retention in infants with pulmonary disease, Synagis has become the drug of choice.
Recommended guidelines for the Synagis treatment regimen are shown in Table 2.
Latest Study News
Data presented at the American Academy of Pediatrics 2002 meeting in October in Boston indicates that Synagis is safe and effective in preventing RSV-related hospitalizations in young children with congenital heart disease (CHD). This was the result of a large, multi-national phase 3 clinical study. The study was a 4-year, double blind, placebo-controlled study designed to assess the safety and efficacy of Synagis in children less than 2 years of age with serious CHD. It was carried out in 76 centers in North America and Europe since 1998.
A total of 1,287 children were randomized to receive five monthly IM injections of either Synagis or a placebo during the RSV season. When compared, the Synagis group had 45 per.cent less hospitalizations due to RSV. The data also showed fewer days of increased oxygen usage in the treated group than the placebo group.
There are approximately 32,000 children born in the United States each year with CHD. Children with CHD who are hospitalized with RSV have a 2 to 6 times greater mortality rate than children without RSV who also are hospitalized with CHD.11
Monitoring Lab RSV Data
RSV activity is monitored in the United States by the National Respiratory and Enteric Virus Surveillance System (NREVSS). This laboratory-based system monitors temporal and geographic patterns associated with the detection of RSV, human parainfluenza viruses, respiratory and enteric adenoviruses, and rotovirus.12
It gathers weekly data on virus detection, iso.lations and electron microscopy results from university and community hospital laboratories, selected state and county public health laboratories, and commercial laboratories that have agreed to participate. From the data it can determine a pattern of RSV activity across the country.
Healthcare practitioners can use the data in these reports in the prevention, treatment and control of RSV. By studying the information for their region, they can implement specific preventive measures and plan for the optimal timing of RSV prophylaxis. Information and links to this and other CDC reports can be found on its Web site: www.cdc.gov.